{$ifndef VER2_4}
{ TEncoding }

class function TEncoding.GetANSI: TEncoding;
begin
  if not Assigned(FStandardEncodings[seAnsi]) then
    FStandardEncodings[seAnsi] := TMBCSEncoding.Create(DefaultSystemCodePage);
  Result := FStandardEncodings[seAnsi];
end;

class function TEncoding.GetASCII: TEncoding;
begin
  if not Assigned(FStandardEncodings[seAscii]) then
    FStandardEncodings[seAscii] := TMBCSEncoding.Create(CP_ASCII);
  Result := FStandardEncodings[seAscii];
end;

class function TEncoding.GetBigEndianUnicode: TEncoding;
begin
  if not Assigned(FStandardEncodings[seBigEndianUnicode]) then
    FStandardEncodings[seBigEndianUnicode] := TBigEndianUnicodeEncoding.Create;
  Result := FStandardEncodings[seBigEndianUnicode];
end;

class function TEncoding.GetDefault: TEncoding;
begin
  Result := GetANSI;
end;

class function TEncoding.GetUnicode: TEncoding;
begin
  if not Assigned(FStandardEncodings[seUnicode]) then
    FStandardEncodings[seUnicode] := TUnicodeEncoding.Create;
  Result := FStandardEncodings[seUnicode];
end;

class function TEncoding.GetUTF7: TEncoding;
begin
  if not Assigned(FStandardEncodings[seUTF7]) then
    FStandardEncodings[seUTF7] := TUTF7Encoding.Create;
  Result := FStandardEncodings[seUTF7];
end;

class function TEncoding.GetUTF8: TEncoding;
begin
  if not Assigned(FStandardEncodings[seUTF8]) then
    FStandardEncodings[seUTF8] := TUTF8Encoding.Create;
  Result := FStandardEncodings[seUTF8];
end;

class procedure TEncoding.FreeEncodings;
var
  E: TStandardEncoding;
begin
  for E := Low(FStandardEncodings) to High(FStandardEncodings) do
    FStandardEncodings[E].Free;
end;

class constructor TEncoding.Create;
var
  E: TStandardEncoding;
begin
  for E := Low(FStandardEncodings) to High(FStandardEncodings) do
    FStandardEncodings[E] := nil;
end;

class destructor TEncoding.Destroy;
begin
  FreeEncodings;
end;

function TEncoding.Clone: TEncoding;
begin
  Result := nil;
end;

class function TEncoding.Convert(Source, Destination: TEncoding;
  const Bytes: TBytes): TBytes;
begin
  Result := Destination.GetBytes(Source.GetChars(Bytes));
end;

class function TEncoding.Convert(Source, Destination: TEncoding;
  const Bytes: TBytes; StartIndex, Count: Integer): TBytes;
begin
  Result := Destination.GetBytes(Source.GetChars(Bytes, StartIndex, Count));
end;

class function TEncoding.IsStandardEncoding(AEncoding: TEncoding): Boolean;
var
  Encoding: TEncoding;
begin
  if Assigned(AEncoding) then
    for Encoding in FStandardEncodings do
      if Encoding = AEncoding then
        Exit(True);
  Result := False;
end;

class function TEncoding.GetBufferEncoding(const Buffer: TBytes; var AEncoding: TEncoding): Integer;
begin
  Result := GetBufferEncoding(Buffer, AEncoding, Default);
end;

class function TEncoding.GetBufferEncoding(const Buffer: TBytes;
  var AEncoding: TEncoding; ADefaultEncoding: TEncoding): Integer;

  function CheckEncoding(AEncoding: TEncoding; out ByteCount: Integer): Boolean;
  var
    Preamble: TBytes;
  begin
    Preamble := AEncoding.GetPreamble;
    ByteCount := Length(Preamble);
    Result := (Length(Buffer) >= ByteCount) and (ByteCount > 0);
    if Result then
      Result := CompareMem(@Preamble[0], @Buffer[0], ByteCount);
  end;

begin
  if Assigned(AEncoding) then
  begin
    if not CheckEncoding(AEncoding, Result) then
      Result := 0;
  end
  else
  if CheckEncoding(Unicode, Result) then
    AEncoding := Unicode
  else
  if CheckEncoding(BigEndianUnicode, Result) then
    AEncoding := BigEndianUnicode
  else
  if CheckEncoding(UTF8, Result) then
    AEncoding := UTF8
  else
  begin
    AEncoding := ADefaultEncoding;
    Result := 0;
  end;
end;

function TEncoding.GetByteCount(const Chars: TUnicodeCharArray): Integer;
begin
  Result := GetByteCount(Chars, 0, Length(Chars));
end;

function TEncoding.GetByteCount(const Chars: TUnicodeCharArray; CharIndex,
  CharCount: Integer): Integer;
begin
  if (CharCount < 0) or (Length(Chars) <= CharCount + CharIndex) then
    raise EEncodingError.CreateFmt(SInvalidCount, [CharCount]);
  if (CharIndex < 0) then
    raise EEncodingError.CreateFmt(SCharacterIndexOutOfBounds, [CharIndex]);
  Result := GetByteCount(@Chars[CharIndex], CharCount);
end;

function TEncoding.GetByteCount(const S: UnicodeString): Integer;
begin
  Result := GetByteCount(PUnicodeChar(S), Length(S));
end;

function TEncoding.GetByteCount(const S: UnicodeString; CharIndex, CharCount: Integer): Integer;
begin
  if (CharCount < 0) or (Length(S) < CharCount + CharIndex) then
    raise EEncodingError.CreateFmt(SInvalidCount, [CharCount]);
  if (CharIndex < 1) then
    raise EEncodingError.CreateFmt(SCharacterIndexOutOfBounds, [CharIndex]);
  Result := GetByteCount(@S[CharIndex], CharCount);
end;

function TEncoding.GetBytes(const Chars: TUnicodeCharArray): TBytes;
begin
  SetLength(Result, GetByteCount(Chars));
  GetBytes(@Chars[0], Length(Chars), @Result[0], Length(Result));
end;

function TEncoding.GetBytes(const Chars: TUnicodeCharArray; CharIndex,
  CharCount: Integer): TBytes;
begin
  if (CharCount < 0) or (Length(Chars) <= CharCount + CharIndex) then
    raise EEncodingError.CreateFmt(SInvalidCount, [CharCount]);
  if (CharIndex < 0) then
    raise EEncodingError.CreateFmt(SCharacterIndexOutOfBounds, [CharIndex]);
  SetLength(Result, GetByteCount(Chars, CharIndex, CharCount));
  GetBytes(@Chars[CharIndex], CharCount, @Result[0], Length(Result));
end;

function TEncoding.GetBytes(const Chars: TUnicodeCharArray; CharIndex,
  CharCount: Integer; const Bytes: TBytes; ByteIndex: Integer): Integer;
var
  ByteLen: Integer;
begin
  ByteLen := Length(Bytes);
  if (ByteLen = 0) and (CharCount > 0) then
    raise EEncodingError.Create(SInvalidDestinationArray);
  if (ByteIndex < 0) or (ByteLen < ByteIndex) then
    raise EEncodingError.CreateFmt(SInvalidDestinationIndex, [ByteIndex]);
  if (CharCount < 0) or (Length(Chars) <= CharCount + CharIndex) then
    raise EEncodingError.CreateFmt(SInvalidCount, [CharCount]);
  if (CharIndex < 0) then
    raise EEncodingError.CreateFmt(SCharacterIndexOutOfBounds, [CharIndex]);
  Result := GetBytes(@Chars[CharIndex], CharCount, @Bytes[ByteIndex], ByteLen - ByteIndex);
end;

function TEncoding.GetBytes(const S: UnicodeString): TBytes;
begin
  SetLength(Result, GetByteCount(S));
  GetBytes(@S[1], Length(S), @Result[0], Length(Result));
end;

function TEncoding.GetBytes(const S: UnicodeString; CharIndex, CharCount: Integer;
  const Bytes: TBytes; ByteIndex: Integer): Integer;
var
  ByteLen: Integer;
begin
  ByteLen := Length(Bytes);
  if (ByteLen = 0) and (CharCount > 0) then
    raise EEncodingError.Create(SInvalidDestinationArray);
  if (ByteIndex < 0) or (ByteLen < ByteIndex) then
    raise EEncodingError.CreateFmt(SInvalidDestinationIndex, [ByteIndex]);
  if (CharCount < 0) or (Length(S) < CharCount + CharIndex) then
    raise EEncodingError.CreateFmt(SInvalidCount, [CharCount]);
  if (CharIndex < 1) then
    raise EEncodingError.CreateFmt(SCharacterIndexOutOfBounds, [CharIndex]);
  Result := GetBytes(@S[CharIndex], CharCount, @Bytes[ByteIndex], ByteLen - ByteIndex);
end;

function TEncoding.GetCharCount(const Bytes: TBytes): Integer;
begin
  Result := GetCharCount(@Bytes[0], Length(Bytes));
end;

function TEncoding.GetCharCount(const Bytes: TBytes; ByteIndex,
  ByteCount: Integer): Integer;
begin
  if (ByteIndex < 0) or (Length(Bytes) < ByteIndex) then
    raise EEncodingError.CreateFmt(SInvalidDestinationIndex, [ByteIndex]);
  Result := GetCharCount(@Bytes[ByteIndex], ByteCount);
end;

function TEncoding.GetChars(const Bytes: TBytes): TUnicodeCharArray;
begin
  SetLength(Result, GetCharCount(Bytes));
  GetChars(@Bytes[0], Length(Bytes), @Result[0], Length(Result));
end;

function TEncoding.GetChars(const Bytes: TBytes; ByteIndex, ByteCount: Integer): TUnicodeCharArray;
begin
  if (ByteIndex < 0) or (Length(Bytes) < ByteIndex) then
    raise EEncodingError.CreateFmt(SInvalidDestinationIndex, [ByteIndex]);
  SetLength(Result, GetCharCount(Bytes, ByteIndex, ByteCount));
  GetChars(@Bytes[ByteIndex], ByteCount, @Result[0], Length(Result));
end;

function TEncoding.GetChars(const Bytes: TBytes; ByteIndex, ByteCount: Integer;
  const Chars: TUnicodeCharArray; CharIndex: Integer): Integer;
var
  CharLen: Integer;
begin
  if (ByteIndex < 0) or (Length(Bytes) <= ByteIndex) then
    raise EEncodingError.CreateFmt(SInvalidDestinationIndex, [ByteIndex]);
  CharLen := Length(Chars);
  if (CharIndex < 0) or (CharLen <= CharIndex) then
    raise EEncodingError.CreateFmt(SCharacterIndexOutOfBounds, [CharIndex]);
  Result := GetChars(@Bytes[ByteIndex], ByteCount, @Chars[CharIndex], CharLen - CharIndex);
end;

class function TEncoding.GetEncoding(CodePage: Integer): TEncoding;
begin
  case CodePage of
    CP_UTF16: Result := TUnicodeEncoding.Create;
    CP_UTF16BE: Result := TBigEndianUnicodeEncoding.Create;
    CP_UTF7: Result := TUTF7Encoding.Create;
    CP_UTF8: Result := TUTF8Encoding.Create;
  else
    Result := TMBCSEncoding.Create(CodePage);
  end;
end;

class function TEncoding.GetEncoding(const EncodingName: UnicodeString): TEncoding;
var
  ACodePage: TSystemCodePage;
begin
  ACodePage := CodePageNameToCodePage(EncodingName);
  if ACodePage = $FFFF then
    raise EEncodingError.CreateFmt(SNotValidCodePageName, [EncodingName]);
  Result := TMBCSEncoding.Create(ACodePage);
end;

function TEncoding.GetString(const Bytes: TBytes): UnicodeString;
var
  Chars: TUnicodeCharArray;
begin
  Chars := GetChars(Bytes);
  SetString(Result, PUnicodeChar(Chars), Length(Chars));
end;

function TEncoding.GetString(const Bytes: TBytes; ByteIndex, ByteCount: Integer): UnicodeString;
var
  Chars: TUnicodeCharArray;
begin
  Chars := GetChars(Bytes, ByteIndex, ByteCount);
  SetString(Result, PUnicodeChar(Chars), Length(Chars));
end;

{ TMBCSEncoding }

function TMBCSEncoding.GetByteCount(Chars: PUnicodeChar; CharCount: Integer): Integer;
var
  S: RawByteString;
begin
  widestringmanager.Unicode2AnsiMoveProc(Chars, S, CodePage, CharCount);
  Result := Length(S);
end;

function TMBCSEncoding.GetBytes(Chars: PUnicodeChar; CharCount: Integer; Bytes: PByte;
  ByteCount: Integer): Integer;
var
  S: RawByteString;
begin
  widestringmanager.Unicode2AnsiMoveProc(Chars, S, CodePage, CharCount);
  Result := Length(S);
  if ByteCount < Result then
    Result := ByteCount;
  if Result > 0 then
    Move(S[1], Bytes[0], Result);
end;

function TMBCSEncoding.GetCharCount(Bytes: PByte; ByteCount: Integer): Integer;
var
  U: UnicodeString;
begin
  widestringmanager.Ansi2UnicodeMoveProc(PChar(Bytes), CodePage, U, ByteCount);
  Result := Length(U);
end;

function TMBCSEncoding.GetChars(Bytes: PByte; ByteCount: Integer; Chars: PUnicodeChar;
  CharCount: Integer): Integer;
var
  U: UnicodeString;
begin
  widestringmanager.Ansi2UnicodeMoveProc(PChar(Bytes), CodePage, U, ByteCount);
  Result := Length(U);
  if CharCount < Result then
    Result := CharCount;
  if Result > 0 then
    Move(U[1], Chars[0], Result * SizeOf(UnicodeChar));
end;

function TMBCSEncoding.GetCodePage: Cardinal;
begin
  Result := FCodePage;
end;

function TMBCSEncoding.GetEncodingName: UnicodeString;
begin
  Result := CodePageToCodePageName(CodePage);
end;

constructor TMBCSEncoding.Create;
begin
  Create(DefaultSystemCodePage, 0, 0);
end;

constructor TMBCSEncoding.Create(ACodePage: Integer);
begin
  Create(ACodePage, 0, 0);
end;

constructor TMBCSEncoding.Create(ACodePage, MBToWCharFlags,
  WCharToMBFlags: Integer);
begin
  FCodePage := ACodePage;
  FMBToWCharFlags := MBToWCharFlags;
  FWCharToMBFlags := WCharToMBFlags;
end;

function TMBCSEncoding.Clone: TEncoding;
begin
  Result := TMBCSEncoding.Create(FCodePage, FMBToWCharFlags, FWCharToMBFlags);
end;

function TMBCSEncoding.GetMaxByteCount(CharCount: Integer): Integer;
begin
  Result := CharCount;
end;

function TMBCSEncoding.GetMaxCharCount(ByteCount: Integer): Integer;
begin
  Result := ByteCount;
end;

function TMBCSEncoding.GetPreamble: TBytes;
begin
  Result := nil;
end;

{ TUTF7Encoding }

constructor TUTF7Encoding.Create;
begin
  inherited Create(CP_UTF7);
  FIsSingleByte := False;
end;

function TUTF7Encoding.Clone: TEncoding;
begin
  Result := TUTF7Encoding.Create;
end;

function TUTF7Encoding.GetMaxByteCount(CharCount: Integer): Integer;
begin
  Result := CharCount * 3 + 2;
end;

function TUTF7Encoding.GetMaxCharCount(ByteCount: Integer): Integer;
begin
  Result := ByteCount;
end;

{ TUTF8Encoding }

constructor TUTF8Encoding.Create;
begin
  inherited Create(CP_UTF8);
  FIsSingleByte := False;
end;

function TUTF8Encoding.Clone: TEncoding;
begin
  Result := TUTF8Encoding.Create;
end;

function TUTF8Encoding.GetMaxByteCount(CharCount: Integer): Integer;
begin
  Result := CharCount * 3;
end;

function TUTF8Encoding.GetMaxCharCount(ByteCount: Integer): Integer;
begin
  Result := ByteCount;
end;

function TUTF8Encoding.GetPreamble: TBytes;
begin
  SetLength(Result, 3);
  Result[0] := $EF;
  Result[1] := $BB;
  Result[2] := $BF;
end;

{ TUnicodeEncoding }

function TUnicodeEncoding.GetByteCount(Chars: PUnicodeChar; CharCount: Integer): Integer;
begin
  Result := CharCount * SizeOf(UnicodeChar);
end;

function TUnicodeEncoding.GetBytes(Chars: PUnicodeChar; CharCount: Integer;
  Bytes: PByte; ByteCount: Integer): Integer;
begin
  Result := CharCount * SizeOf(UnicodeChar);
  if ByteCount < Result then
    Result := ByteCount;
  if Result > 0 then
    Move(Chars[0], Bytes[0], Result);
end;

function TUnicodeEncoding.GetCharCount(Bytes: PByte; ByteCount: Integer): Integer;
begin
  Result := ByteCount div SizeOf(UnicodeChar);
end;

function TUnicodeEncoding.GetChars(Bytes: PByte; ByteCount: Integer;
  Chars: PUnicodeChar; CharCount: Integer): Integer;
begin
  Result := ByteCount div 2;
  if CharCount < Result then
    Result := CharCount;
  Move(Bytes[0], Chars[0], Result * SizeOf(UnicodeChar));
end;

function TUnicodeEncoding.GetCodePage: Cardinal;
begin
  Result := CP_UTF16;
end;

function TUnicodeEncoding.GetEncodingName: UnicodeString;
begin
  Result := CodePageToCodePageName(CodePage);
end;

constructor TUnicodeEncoding.Create;
begin
  inherited Create;
  FIsSingleByte := False;
  FMaxCharSize := SizeOf(UnicodeChar);
end;

function TUnicodeEncoding.Clone: TEncoding;
begin
  Result := TUnicodeEncoding.Create;
end;

function TUnicodeEncoding.GetMaxByteCount(CharCount: Integer): Integer;
begin
  Result := CharCount * SizeOf(UnicodeChar);
end;

function TUnicodeEncoding.GetMaxCharCount(ByteCount: Integer): Integer;
begin
  Result := ByteCount div SizeOf(UnicodeChar);
end;

function TUnicodeEncoding.GetPreamble: TBytes;
begin
  SetLength(Result, 2);
  Result[0] := $FF;
  Result[1] := $FE;
end;

{ TBigEndianUnicodeEncoding }

function TBigEndianUnicodeEncoding.GetBytes(Chars: PUnicodeChar; CharCount: Integer;
  Bytes: PByte; ByteCount: Integer): Integer;
var
  LastByte: PByte;
begin
  Result := CharCount * SizeOf(UnicodeChar);
  if ByteCount < Result then
    Result := ByteCount;
  LastByte := @Bytes[Result];
  while Bytes < LastByte do
  begin
    Bytes^ := Hi(Word(Chars^));
    inc(Bytes);
    if Bytes < LastByte then
      Bytes^ := Lo(Word(Chars^));
    inc(Bytes);
    inc(Chars);
  end;
end;

function TBigEndianUnicodeEncoding.GetChars(Bytes: PByte; ByteCount: Integer;
  Chars: PUnicodeChar; CharCount: Integer): Integer;
var
  LastChar: PUnicodeChar;
begin
  Result := ByteCount div SizeOf(UnicodeChar);
  if CharCount < Result then
    Result := CharCount;
  LastChar := @Chars[Result];
  while Chars <= LastChar do
  begin
    Chars^ := UnicodeChar(Bytes[1] + Bytes[0] shl 8);
    inc(Bytes, SizeOf(UnicodeChar));
    inc(Chars);
  end;
end;

function TBigEndianUnicodeEncoding.GetCodePage: Cardinal;
begin
  Result := CP_UTF16BE;
end;

function TBigEndianUnicodeEncoding.GetEncodingName: UnicodeString;
begin
  Result := CodePageToCodePageName(CodePage);
end;

function TBigEndianUnicodeEncoding.Clone: TEncoding;
begin
  Result := TBigEndianUnicodeEncoding.Create;
end;

function TBigEndianUnicodeEncoding.GetPreamble: TBytes;
begin
  SetLength(Result, 2);
  Result[0] := $FE;
  Result[1] := $FF;
end;
{$endif VER2_4}